Find area bounded by self-intersecting array of data

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Rchamp 2021-3-14

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https://ww2.mathworks.cn/matlabcentral/answers/772823-find-area-bounded-by-self-intersecting-array-of-data

回答： Nipun 2024-6-7

I'm trying to find work from a PV diagram, thus I need to find the area bounded by my curve created by an array of data. Specifically, I need to find the area of the top enclosed curve, minus the area of the bottom enclosed curve. See the attached picture for more. I've tried using this function to find intersections of my data in order to split up the top and bottom enclosed curves but it returns ~110 intersections. I have also tried using polyarea but its giving me a result that is obviosly untrue (4*10^3), and I can't find a way for it to visually show me what area it is using in its calculations. Could anyone help me with this? Thanks!

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darova 2021-3-15

Can you show on the picture are you want to calculate?

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Answer 1

Nipun 2024-6-7

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Hi Rchamp,

I understand that you want to find the area bounded by your curve from a PV diagram, specifically the area of the top enclosed curve minus the area of the bottom enclosed curve. Here's an approach using MATLAB:

% Assuming your data is in x and y vectors
x = ...; % your x data
y = ...; % your y data
% Find the intersections of the curves
[xa, ya] = intersections(x, y);
% Split the data into two separate curves
topCurveX = x(x <= xa(1));
topCurveY = y(x <= xa(1));
bottomCurveX = x(x >= xa(2));
bottomCurveY = y(x >= xa(2));
% Calculate the areas
areaTop = trapz(topCurveX, topCurveY);
areaBottom = trapz(bottomCurveX, bottomCurveY);
% Calculate the enclosed area
enclosedArea = areaTop - areaBottom;
% Display the result
disp(['Enclosed Area: ', num2str(enclosedArea)]);